Weirs are hydraulic structures that used in flood traort, adjust the water level, flow measurement and drainage channels widely. Use of labyrinth weirs is one of the most effective and economical way to increase the effective length of crest. These spillways by a broken axe on the plan are defined. The length of the crest in labyrinth weir is greater than normal weir. Triangular labyrinth weir is more efficient than other labyrinth weirs. The researchers found that, performance of triangular labyrinth weir is reduced when the discharge increased. In this study, submerged guide vanes are used in upstream of the triangular labyrinth weir with ?=45(? is labyrinth side weir included angle). 3 widths for the submerged guide vanes are considered. They are equal to one, 2 and 3 centimeter. These models have different configurations and used to the number one upto 6 vanes that situated the upstream overflow wall. These tests have been done on free flow condition for 4 discharges. About wider vanes use of two vanes on the elementary quarter axis and middle axis have lower discharge coefficient than one vane. The highest percentage increase in discharge coefficient occurs at the highest discharge. So the impact of the submerged guide vanes in high discharge is more. This result is correspond to previous researches. Second, regardless of the width of the vane, the model with one vane on the middle axis and the model with one vane on the elementary quarter axis and other vane on the last quarter axis, with 18.34% increase in discharge coefficient are best models. Water surface profiles show that the upstream head of the submerged guide vanes with 3 centimeter width is more than others. The results of cross profiles showed that the upstream submerged guide vanes cause more fluctuations in water level. Finally, an optimal equation was offered to calculate the weir discharge coefficient of the triangular labyrinth weir with submerged guide vanes by software.
